/*====================================================================*
 -  Copyright (C) 2001 Leptonica.  All rights reserved.
 -
 -  Redistribution and use in source and binary forms, with or without
 -  modification, are permitted provided that the following conditions
 -  are met:
 -  1. Redistributions of source code must retain the above copyright
 -     notice, this list of conditions and the following disclaimer.
 -  2. Redistributions in binary form must reproduce the above
 -     copyright notice, this list of conditions and the following
 -     disclaimer in the documentation and/or other materials
 -     provided with the distribution.
 -
 -  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 -  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 -  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 -  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL ANY
 -  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 -  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 -  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 -  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 -  OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 -  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 -  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *====================================================================*/

/*!
 * \file enhance.c
 * <pre>
 *
 *      Gamma TRC (tone reproduction curve) mapping
 *           PIX     *pixGammaTRC()
 *           PIX     *pixGammaTRCMasked()
 *           PIX     *pixGammaTRCWithAlpha()
 *           NUMA    *numaGammaTRC()
 *
 *      Contrast enhancement
 *           PIX     *pixContrastTRC()
 *           PIX     *pixContrastTRCMasked()
 *           NUMA    *numaContrastTRC()
 *
 *      Histogram equalization
 *           PIX     *pixEqualizeTRC()
 *           NUMA    *numaEqualizeTRC()
 *
 *      Generic TRC mapper
 *           l_int32  pixTRCMap()
 *           l_int32  pixTRCMapGeneral()
 *
 *      Unsharp-masking
 *           PIX     *pixUnsharpMasking()
 *           PIX     *pixUnsharpMaskingGray()
 *           PIX     *pixUnsharpMaskingFast()
 *           PIX     *pixUnsharpMaskingGrayFast()
 *           PIX     *pixUnsharpMaskingGray1D()
 *           PIX     *pixUnsharpMaskingGray2D()
 *
 *      Hue and saturation modification
 *           PIX     *pixModifyHue()
 *           PIX     *pixModifySaturation()
 *           l_int32  pixMeasureSaturation()
 *           PIX     *pixModifyBrightness()
 *
 *      Color shifting
 *           PIX     *pixMosaicColorShiftRGB()
 *           PIX     *pixColorShiftRGB()
 *
 *      Darken gray (unsaturated) pixels
 *           PIX     *pixDarkenGray()
 *
 *      General multiplicative constant color transform
 *           PIX     *pixMultConstantColor()
 *           PIX     *pixMultMatrixColor()
 *
 *      Edge by bandpass
 *           PIX     *pixHalfEdgeByBandpass()
 *
 *      Gamma correction, contrast enhancement and histogram equalization
 *      apply a simple mapping function to each pixel (or, for color
 *      images, to each sample (i.e., r,g,b) of the pixel).
 *
 *       ~ Gamma correction either lightens the image or darkens
 *         it, depending on whether the gamma factor is greater
 *         or less than 1.0, respectively.
 *
 *       ~ Contrast enhancement darkens the pixels that are already
 *         darker than the middle of the dynamic range (128)
 *         and lightens pixels that are lighter than 128.
 *
 *       ~ Histogram equalization remaps to have the same number
 *         of image pixels at each of 256 intensity values.  This is
 *         a quick and dirty method of adjusting contrast and brightness
 *         to bring out details in both light and dark regions.
 *
 *      Unsharp masking is a more complicated enhancement.
 *      A "high frequency" image, generated by subtracting
 *      the smoothed ("low frequency") part of the image from
 *      itself, has all the energy at the edges.  This "edge image"
 *      has 0 average value.  A fraction of the edge image is
 *      then added to the original, enhancing the differences
 *      between pixel values at edges.  Because we represent
 *      images as l_uint8 arrays, we preserve dynamic range and
 *      handle negative values by doing all the arithmetic on
 *      shifted l_uint16 arrays; the l_uint8 values are recovered
 *      at the end.
 *
 *      Hue and saturation modification work in HSV space.  Because
 *      this is too large for efficient table lookup, each pixel value
 *      is transformed to HSV, modified, and transformed back.
 *      It's not the fastest way to do this, but the method is
 *      easily understood.
 *
 *      Unsharp masking is never in-place, and returns a clone if no
 *      operation is to be performed.
 * </pre>
 */

#ifdef HAVE_CONFIG_H
#include <config_auto.h>
#endif  /* HAVE_CONFIG_H */

#include <math.h>
#include "allheaders.h"

    /* Scales contrast enhancement factor to have a useful range
     * between 0.0 and 1.0 */
static const l_float32  EnhanceScaleFactor = 5.0;

/*-------------------------------------------------------------*
 *         Gamma TRC (tone reproduction curve) mapping         *
 *-------------------------------------------------------------*/
/*!
 * \brief   pixGammaTRC()
 *
 * \param[in]    pixd     [optional] null or equal to pixs
 * \param[in]    pixs     8 or 32 bpp; or 2, 4 or 8 bpp with colormap
 * \param[in]    gamma    gamma correction; must be > 0.0
 * \param[in]    minval   input value that gives 0 for output; can be < 0
 * \param[in]    maxval   input value that gives 255 for output; can be > 255
 * \return  pixd always
 *
 * <pre>
 * Notes:
 *      (1) pixd must either be null or equal to pixs.
 *          For in-place operation, set pixd == pixs:
 *             pixGammaTRC(pixs, pixs, ...);
 *          To get a new image, set pixd == null:
 *             pixd = pixGammaTRC(NULL, pixs, ...);
 *      (2) If pixs is colormapped, the colormap is transformed,
 *          either in-place or in a copy of pixs.
 *      (3) We use a gamma mapping between minval and maxval.
 *      (4) If gamma < 1.0, the image will appear darker;
 *          if gamma > 1.0, the image will appear lighter;
 *      (5) If gamma = 1.0 and minval = 0 and maxval = 255, no
 *          enhancement is performed; return a copy unless in-place,
 *          in which case this is a no-op.
 *      (6) For color images that are not colormapped, the mapping
 *          is applied to each component.
 *      (7) minval and maxval are not restricted to the interval [0, 255].
 *          If minval < 0, an input value of 0 is mapped to a
 *          nonzero output.  This will turn black to gray.
 *          If maxval > 255, an input value of 255 is mapped to
 *          an output value less than 255.  This will turn
 *          white (e.g., in the background) to gray.
 *      (8) Increasing minval darkens the image.
 *      (9) Decreasing maxval bleaches the image.
 *      (10) Simultaneously increasing minval and decreasing maxval
 *           will darken the image and make the colors more intense;
 *           e.g., minval = 50, maxval = 200.
 *      (11) See numaGammaTRC() for further examples of use.
 *      (12) Use pixTRCMapGeneral() if applying different mappings
 *           to each channel in an RGB image.
 * </pre>
 */
PIX *
pixGammaTRC(PIX       *pixd,
            PIX       *pixs,
            l_float32  gamma,
            l_int32    minval,
            l_int32    maxval)
{
l_int32   d;
NUMA     *nag;
PIXCMAP  *cmap;

    PROCNAME("pixGammaTRC");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, pixd);
    if (pixd && (pixd != pixs))
        return (PIX *)ERROR_PTR("pixd not null or pixs", procName, pixd);
    if (gamma <= 0.0) {
        L_WARNING("gamma must be > 0.0; setting to 1.0\n", procName);
        gamma = 1.0;
    }
    if (minval >= maxval)
        return (PIX *)ERROR_PTR("minval not < maxval", procName, pixd);
    cmap = pixGetColormap(pixs);
    d = pixGetDepth(pixs);
    if (!cmap && d != 8 && d != 32)
        return (PIX *)ERROR_PTR("depth not 8 or 32 bpp", procName, pixd);

    if (gamma == 1.0 && minval == 0 && maxval == 255)  /* no-op */
        return pixCopy(pixd, pixs);

    if (!pixd)  /* start with a copy if not in-place */
        pixd = pixCopy(NULL, pixs);

    if (cmap) {
        pixcmapGammaTRC(pixGetColormap(pixd), gamma, minval, maxval);
        return pixd;
    }

        /* pixd is 8 or 32 bpp */
    if ((nag = numaGammaTRC(gamma, minval, maxval)) == NULL)
        return (PIX *)ERROR_PTR("nag not made", procName, pixd);
    pixTRCMap(pixd, NULL, nag);
    numaDestroy(&nag);

    return pixd;
}


/*!
 * \brief   pixGammaTRCMasked()
 *
 * \param[in]    pixd      [optional] null or equal to pixs
 * \param[in]    pixs      8 or 32 bpp; not colormapped
 * \param[in]    pixm      [optional] null or 1 bpp
 * \param[in]    gamma     gamma correction; must be > 0.0
 * \param[in]    minval    input value that gives 0 for output; can be < 0
 * \param[in]    maxval    input value that gives 255 for output; can be > 255
 * \return  pixd always
 *
 * <pre>
 * Notes:
 *      (1) Same as pixGammaTRC() except mapping is optionally over
 *          a subset of pixels described by pixm.
 *      (2) Masking does not work for colormapped images.
 *      (3) See pixGammaTRC() for details on how to use the parameters.
 * </pre>
 */
PIX *
pixGammaTRCMasked(PIX       *pixd,
                  PIX       *pixs,
                  PIX       *pixm,
                  l_float32  gamma,
                  l_int32    minval,
                  l_int32    maxval)
{
l_int32  d;
NUMA    *nag;

    PROCNAME("pixGammaTRCMasked");

    if (!pixm)
        return pixGammaTRC(pixd, pixs, gamma, minval, maxval);

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, pixd);
    if (pixGetColormap(pixs))
        return (PIX *)ERROR_PTR("invalid: pixs has a colormap", procName, pixd);
    if (pixd && (pixd != pixs))
        return (PIX *)ERROR_PTR("pixd not null or pixs", procName, pixd);
    d = pixGetDepth(pixs);
    if (d != 8 && d != 32)
        return (PIX *)ERROR_PTR("depth not 8 or 32 bpp", procName, pixd);
    if (minval >= maxval)
        return (PIX *)ERROR_PTR("minval not < maxval", procName, pixd);
    if (gamma <= 0.0) {
        L_WARNING("gamma must be > 0.0; setting to 1.0\n", procName);
        gamma = 1.0;
    }

    if (gamma == 1.0 && minval == 0 && maxval == 255)
        return pixCopy(pixd, pixs);

    if (!pixd)  /* start with a copy if not in-place */
        pixd = pixCopy(NULL, pixs);

    if ((nag = numaGammaTRC(gamma, minval, maxval)) == NULL)
        return (PIX *)ERROR_PTR("nag not made", procName, pixd);
    pixTRCMap(pixd, pixm, nag);
    numaDestroy(&nag);

    return pixd;
}


/*!
 * \brief   pixGammaTRCWithAlpha()
 *
 * \param[in]    pixd     [optional] null or equal to pixs
 * \param[in]    pixs     32 bpp
 * \param[in]    gamma    gamma correction; must be > 0.0
 * \param[in]    minval   input value that gives 0 for output; can be < 0
 * \param[in]    maxval   input value that gives 255 for output; can be > 255
 * \return  pixd always
 *
 * <pre>
 * Notes:
 *      (1) See usage notes in pixGammaTRC().
 *      (2) This version saves the alpha channel.  It is only valid
 *          for 32 bpp (no colormap), and is a bit slower.
 * </pre>
 */
PIX *
pixGammaTRCWithAlpha(PIX       *pixd,
                     PIX       *pixs,
                     l_float32  gamma,
                     l_int32    minval,
                     l_int32    maxval)
{
NUMA  *nag;
PIX   *pixalpha;

    PROCNAME("pixGammaTRCWithAlpha");

    if (!pixs || pixGetDepth(pixs) != 32)
        return (PIX *)ERROR_PTR("pixs undefined or not 32 bpp", procName, pixd);
    if (pixd && (pixd != pixs))
        return (PIX *)ERROR_PTR("pixd not null or pixs", procName, pixd);
    if (gamma <= 0.0) {
        L_WARNING("gamma must be > 0.0; setting to 1.0\n", procName);
        gamma = 1.0;
    }
    if (minval >= maxval)
        return (PIX *)ERROR_PTR("minval not < maxval", procName, pixd);

    if (gamma == 1.0 && minval == 0 && maxval == 255)
        return pixCopy(pixd, pixs);
    if (!pixd)  /* start with a copy if not in-place */
        pixd = pixCopy(NULL, pixs);

    pixalpha = pixGetRGBComponent(pixs, L_ALPHA_CHANNEL);  /* save */
    if ((nag = numaGammaTRC(gamma, minval, maxval)) == NULL)
        return (PIX *)ERROR_PTR("nag not made", procName, pixd);
    pixTRCMap(pixd, NULL, nag);
    pixSetRGBComponent(pixd, pixalpha, L_ALPHA_CHANNEL);  /* restore */
    pixSetSpp(pixd, 4);

    numaDestroy(&nag);
    pixDestroy(&pixalpha);
    return pixd;
}


/*!
 * \brief   numaGammaTRC()
 *
 * \param[in]    gamma   gamma factor; must be > 0.0
 * \param[in]    minval  input value that gives 0 for output
 * \param[in]    maxval  input value that gives 255 for output
 * \return  na, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) The map is returned as a numa; values are clipped to [0, 255].
 *      (2) For a linear mapping, set gamma = 1.0.
 *      (3) To force all intensities into a range within fraction delta
 *          of white, use: minval = -256 * (1 - delta) / delta
 *                         maxval = 255
 *      (4) To force all intensities into a range within fraction delta
 *          of black, use: minval = 0
 *                         maxval = 256 * (1 - delta) / delta
 * </pre>
 */
NUMA *
numaGammaTRC(l_float32  gamma,
             l_int32    minval,
             l_int32    maxval)
{
l_int32    i, val;
l_float32  x, invgamma;
NUMA      *na;

    PROCNAME("numaGammaTRC");

    if (minval >= maxval)
        return (NUMA *)ERROR_PTR("minval not < maxval", procName, NULL);
    if (gamma <= 0.0) {
        L_WARNING("gamma must be > 0.0; setting to 1.0\n", procName);
        gamma = 1.0;
    }

    invgamma = 1. / gamma;
    na = numaCreate(256);
    for (i = 0; i < minval; i++)
        numaAddNumber(na, 0);
    for (i = minval; i <= maxval; i++) {
        if (i < 0) continue;
        if (i > 255) continue;
        x = (l_float32)(i - minval) / (l_float32)(maxval - minval);
        val = (l_int32)(255. * powf(x, invgamma) + 0.5);
        val = L_MAX(val, 0);
        val = L_MIN(val, 255);
        numaAddNumber(na, val);
    }
    for (i = maxval + 1; i < 256; i++)
        numaAddNumber(na, 255);

    return na;
}


/*-------------------------------------------------------------*
 *                      Contrast enhancement                   *
 *-------------------------------------------------------------*/
/*!
 * \brief   pixContrastTRC()
 *
 * \param[in]    pixd     [optional] null or equal to pixs
 * \param[in]    pixs     8 or 32 bpp; or 2, 4 or 8 bpp with colormap
 * \param[in]    factor   0.0 is no enhancement
 * \return  pixd always
 *
 * <pre>
 * Notes:
 *      (1) pixd must either be null or equal to pixs.
 *          For in-place operation, set pixd == pixs:
 *             pixContrastTRC(pixs, pixs, ...);
 *          To get a new image, set pixd == null:
 *             pixd = pixContrastTRC(NULL, pixs, ...);
 *      (2) If pixs is colormapped, the colormap is transformed,
 *          either in-place or in a copy of pixs.
 *      (3) Contrast is enhanced by mapping each color component
 *          using an atan function with maximum slope at 127.
 *          Pixels below 127 are lowered in intensity and pixels
 *          above 127 are increased.
 *      (4) The useful range for the contrast factor is scaled to
 *          be in (0.0 to 1.0), but larger values can also be used.
 *      (5) If factor == 0.0, no enhancement is performed; return a copy
 *          unless in-place, in which case this is a no-op.
 *      (6) For color images that are not colormapped, the mapping
 *          is applied to each component.
 * </pre>
 */
PIX *
pixContrastTRC(PIX       *pixd,
               PIX       *pixs,
               l_float32  factor)
{
l_int32   d;
NUMA     *nac;
PIXCMAP  *cmap;

    PROCNAME("pixContrastTRC");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, pixd);
    if (pixd && (pixd != pixs))
        return (PIX *)ERROR_PTR("pixd not null or pixs", procName, pixd);
    if (factor < 0.0) {
        L_WARNING("factor must be >= 0.0; using 0.0\n", procName);
        factor = 0.0;
    }
    if (factor == 0.0)
        return pixCopy(pixd, pixs);

    cmap = pixGetColormap(pixs);
    d = pixGetDepth(pixs);
    if (!cmap && d != 8 && d != 32)
        return (PIX *)ERROR_PTR("depth not 8 or 32 bpp", procName, pixd);

    if (!pixd)  /* start with a copy if not in-place */
        pixd = pixCopy(NULL, pixs);

    if (cmap) {
        pixcmapContrastTRC(pixGetColormap(pixd), factor);
        return pixd;
    }

        /* pixd is 8 or 32 bpp */
    if ((nac = numaContrastTRC(factor)) == NULL)
        return (PIX *)ERROR_PTR("nac not made", procName, pixd);
    pixTRCMap(pixd, NULL, nac);
    numaDestroy(&nac);

    return pixd;
}


/*!
 * \brief   pixContrastTRCMasked()
 *
 * \param[in]    pixd     [optional] null or equal to pixs
 * \param[in]    pixs     8 or 32 bpp; or 2, 4 or 8 bpp with colormap
 * \param[in]    pixm     [optional] null or 1 bpp
 * \param[in]    factor   0.0 is no enhancement
 * \return  pixd always
 *
 * <pre>
 * Notes:
 *      (1) Same as pixContrastTRC() except mapping is optionally over
 *          a subset of pixels described by pixm.
 *      (2) Masking does not work for colormapped images.
 *      (3) See pixContrastTRC() for details on how to use the parameters.
 * </pre>
 */
PIX *
pixContrastTRCMasked(PIX       *pixd,
                     PIX       *pixs,
                     PIX       *pixm,
                     l_float32  factor)
{
l_int32  d;
NUMA    *nac;

    PROCNAME("pixContrastTRCMasked");

    if (!pixm)
        return pixContrastTRC(pixd, pixs, factor);

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, pixd);
    if (pixGetColormap(pixs))
        return (PIX *)ERROR_PTR("invalid: pixs has a colormap", procName, pixd);
    if (pixd && (pixd != pixs))
        return (PIX *)ERROR_PTR("pixd not null or pixs", procName, pixd);
    d = pixGetDepth(pixs);
    if (d != 8 && d != 32)
        return (PIX *)ERROR_PTR("depth not 8 or 32 bpp", procName, pixd);

    if (factor < 0.0) {
        L_WARNING("factor must be >= 0.0; using 0.0\n", procName);
        factor = 0.0;
    }
    if (factor == 0.0)
        return pixCopy(pixd, pixs);

    if (!pixd)  /* start with a copy if not in-place */
        pixd = pixCopy(NULL, pixs);

    if ((nac = numaContrastTRC(factor)) == NULL)
        return (PIX *)ERROR_PTR("nac not made", procName, pixd);
    pixTRCMap(pixd, pixm, nac);
    numaDestroy(&nac);

    return pixd;
}


/*!
 * \brief   numaContrastTRC()
 *
 * \param[in]    factor   generally between 0.0 [no enhancement]
 *                        and 1.0, but can be larger than 1.0
 * \return  na, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) The mapping is monotonic increasing, where 0 is mapped
 *          to 0 and 255 is mapped to 255.
 *      (2) As 'factor' is increased from 0.0 (where the mapping is linear),
 *          the map gets closer to its limit as a step function that
 *          jumps from 0 to 255 at the center (input value = 127).
 * </pre>
 */
NUMA *
numaContrastTRC(l_float32  factor)
{
l_int32    i, val;
l_float64  x, ymax, ymin, dely, scale;
NUMA      *na;

    PROCNAME("numaContrastTRC");

    if (factor < 0.0) {
        L_WARNING("factor must be >= 0.0; using 0.0; no enhancement\n",
                  procName);
        factor = 0.0;
    }
    if (factor == 0.0)
        return numaMakeSequence(0, 1, 256);  /* linear map */

    scale = EnhanceScaleFactor;
    ymax = atan((l_float64)(1.0 * factor * scale));
    ymin = atan((l_float64)(-127. * factor * scale / 128.));
    dely = ymax - ymin;
    na = numaCreate(256);
    for (i = 0; i < 256; i++) {
        x = (l_float64)i;
        val = (l_int32)((255. / dely) *
             (-ymin + atan((l_float64)(factor * scale * (x - 127.) / 128.))) +
                 0.5);
        numaAddNumber(na, val);
    }

    return na;
}


/*-------------------------------------------------------------*
 *                     Histogram equalization                  *
 *-------------------------------------------------------------*/
/*!
 * \brief   pixEqualizeTRC()
 *
 * \param[in]    pixd     [optional] null or equal to pixs
 * \param[in]    pixs     8 bpp gray, 32 bpp rgb, or colormapped
 * \param[in]    fract    fraction of equalization movement of pixel values
 * \param[in]    factor   subsampling factor; integer >= 1
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) pixd must either be null or equal to pixs.
 *          For in-place operation, set pixd == pixs:
 *             pixEqualizeTRC(pixs, pixs, ...);
 *          To get a new image, set pixd == null:
 *             pixd = pixEqualizeTRC(NULL, pixs, ...);
 *      (2) In histogram equalization, a tone reproduction curve
 *          mapping is used to make the number of pixels at each
 *          intensity equal.
 *      (3) If fract == 0.0, no equalization is performed; return a copy
 *          unless in-place, in which case this is a no-op.
 *          If fract == 1.0, equalization is complete.
 *      (4) Set the subsampling factor > 1 to reduce the amount of computation.
 *      (5) If pixs is colormapped, the colormap is removed and
 *          converted to rgb or grayscale.
 *      (6) If pixs has color, equalization is done in each channel
 *          separately.
 *      (7) Note that even if there is a colormap, we can get an
 *          in-place operation because the intermediate image pixt
 *          is copied back to pixs (which for in-place is the same
 *          as pixd).
 * </pre>
 */
PIX *
pixEqualizeTRC(PIX       *pixd,
               PIX       *pixs,
               l_float32  fract,
               l_int32    factor)
{
l_int32   d;
NUMA     *na;
PIX      *pixt, *pix8;
PIXCMAP  *cmap;

    PROCNAME("pixEqualizeTRC");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (pixd && (pixd != pixs))
        return (PIX *)ERROR_PTR("pixd not null or pixs", procName, pixd);
    cmap = pixGetColormap(pixs);
    d = pixGetDepth(pixs);
    if (d != 8 && d != 32 && !cmap)
        return (PIX *)ERROR_PTR("pixs not 8/32 bpp or cmapped", procName, NULL);
    if (fract < 0.0 || fract > 1.0)
        return (PIX *)ERROR_PTR("fract not in [0.0 ... 1.0]", procName, NULL);
    if (factor < 1)
        return (PIX *)ERROR_PTR("sampling factor < 1", procName, NULL);

    if (fract == 0.0)
        return pixCopy(pixd, pixs);

        /* If there is a colormap, remove it. */
    if (cmap)
        pixt = pixRemoveColormap(pixs, REMOVE_CMAP_BASED_ON_SRC);
    else
        pixt = pixClone(pixs);

        /* Make a copy if necessary */
    pixd = pixCopy(pixd, pixt);
    pixDestroy(&pixt);

    d = pixGetDepth(pixd);
    if (d == 8) {
        na = numaEqualizeTRC(pixd, fract, factor);
        pixTRCMap(pixd, NULL, na);
        numaDestroy(&na);
    } else {  /* 32 bpp */
        pix8 = pixGetRGBComponent(pixd, COLOR_RED);
        na = numaEqualizeTRC(pix8, fract, factor);
        pixTRCMap(pix8, NULL, na);
        pixSetRGBComponent(pixd, pix8, COLOR_RED);
        numaDestroy(&na);
        pixDestroy(&pix8);
        pix8 = pixGetRGBComponent(pixd, COLOR_GREEN);
        na = numaEqualizeTRC(pix8, fract, factor);
        pixTRCMap(pix8, NULL, na);
        pixSetRGBComponent(pixd, pix8, COLOR_GREEN);
        numaDestroy(&na);
        pixDestroy(&pix8);
        pix8 = pixGetRGBComponent(pixd, COLOR_BLUE);
        na = numaEqualizeTRC(pix8, fract, factor);
        pixTRCMap(pix8, NULL, na);
        pixSetRGBComponent(pixd, pix8, COLOR_BLUE);
        numaDestroy(&na);
        pixDestroy(&pix8);
    }

    return pixd;
}


/*!
 * \brief   numaEqualizeTRC()
 *
 * \param[in]    pix     8 bpp, no colormap
 * \param[in]    fract   fraction of equalization movement of pixel values
 * \param[in]    factor  subsampling factor; integer >= 1
 * \return  nad, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) If fract == 0.0, no equalization will be performed.
 *          If fract == 1.0, equalization is complete.
 *      (2) Set the subsampling factor > 1 to reduce the amount of computation.
 *      (3) The map is returned as a numa with 256 values, specifying
 *          the equalized value (array value) for every input value
 *          (the array index).
 * </pre>
 */
NUMA *
numaEqualizeTRC(PIX       *pix,
                l_float32  fract,
                l_int32    factor)
{
l_int32    iin, iout, itarg;
l_float32  val, sum;
NUMA      *nah, *nasum, *nad;

    PROCNAME("numaEqualizeTRC");

    if (!pix)
        return (NUMA *)ERROR_PTR("pix not defined", procName, NULL);
    if (pixGetDepth(pix) != 8)
        return (NUMA *)ERROR_PTR("pix not 8 bpp", procName, NULL);
    if (fract < 0.0 || fract > 1.0)
        return (NUMA *)ERROR_PTR("fract not in [0.0 ... 1.0]", procName, NULL);
    if (factor < 1)
        return (NUMA *)ERROR_PTR("sampling factor < 1", procName, NULL);

    if (fract == 0.0)
        L_WARNING("fract = 0.0; no equalization requested\n", procName);

    if ((nah = pixGetGrayHistogram(pix, factor)) == NULL)
        return (NUMA *)ERROR_PTR("histogram not made", procName, NULL);
    numaGetSum(nah, &sum);
    nasum = numaGetPartialSums(nah);

    nad = numaCreate(256);
    for (iin = 0; iin < 256; iin++) {
        numaGetFValue(nasum, iin, &val);
        itarg = (l_int32)(255. * val / sum + 0.5);
        iout = iin + (l_int32)(fract * (itarg - iin));
        iout = L_MIN(iout, 255);  /* to be safe */
        numaAddNumber(nad, iout);
    }

    numaDestroy(&nah);
    numaDestroy(&nasum);
    return nad;
}


/*-------------------------------------------------------------*
 *                       Generic TRC mapping                   *
 *-------------------------------------------------------------*/
/*!
 * \brief   pixTRCMap()
 *
 * \param[in]    pixs    8 grayscale or 32 bpp rgb; not colormapped
 * \param[in]    pixm    [optional] 1 bpp mask
 * \param[in]    na      mapping array
 * \return  0 if OK, 1 on error
 *
 * <pre>
 * Notes:
 *      (1) This operation is in-place on pixs.
 *      (2) For 32 bpp, this applies the same map to each of the r,g,b
 *          components.
 *      (3) The mapping array is of size 256, and it maps the input
 *          index into values in the range [0, 255].
 *      (4) If defined, the optional 1 bpp mask pixm has its origin
 *          aligned with pixs, and the map function is applied only
 *          to pixels in pixs under the fg of pixm.
 *      (5) For 32 bpp, this does not save the alpha channel.
 * </pre>
 */
l_int32
pixTRCMap(PIX   *pixs,
          PIX   *pixm,
          NUMA  *na)
{
l_int32    w, h, d, wm, hm, wpl, wplm, i, j, sval8, dval8;
l_uint32   sval32, dval32;
l_uint32  *data, *datam, *line, *linem, *tab;

    PROCNAME("pixTRCMap");

    if (!pixs)
        return ERROR_INT("pixs not defined", procName, 1);
    if (pixGetColormap(pixs))
        return ERROR_INT("pixs is colormapped", procName, 1);
    if (!na)
        return ERROR_INT("na not defined", procName, 1);
    if (numaGetCount(na) != 256)
        return ERROR_INT("na not of size 256", procName, 1);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 8 && d != 32)
        return ERROR_INT("pixs not 8 or 32 bpp", procName, 1);
    if (pixm) {
        if (pixGetDepth(pixm) != 1)
            return ERROR_INT("pixm not 1 bpp", procName, 1);
    }

    tab = (l_uint32 *)numaGetIArray(na);  /* get the array for efficiency */
    wpl = pixGetWpl(pixs);
    data = pixGetData(pixs);
    if (!pixm) {
        if (d == 8) {
            for (i = 0; i < h; i++) {
                line = data + i * wpl;
                for (j = 0; j < w; j++) {
                    sval8 = GET_DATA_BYTE(line, j);
                    dval8 = tab[sval8];
                    SET_DATA_BYTE(line, j, dval8);
                }
            }
        } else {  /* d == 32 */
            for (i = 0; i < h; i++) {
                line = data + i * wpl;
                for (j = 0; j < w; j++) {
                    sval32 = *(line + j);
                    dval32 =
                        tab[(sval32 >> L_RED_SHIFT) & 0xff] << L_RED_SHIFT |
                        tab[(sval32 >> L_GREEN_SHIFT) & 0xff] << L_GREEN_SHIFT |
                        tab[(sval32 >> L_BLUE_SHIFT) & 0xff] << L_BLUE_SHIFT;
                    *(line + j) = dval32;
                }
            }
        }
    } else {
        datam = pixGetData(pixm);
        wplm = pixGetWpl(pixm);
        pixGetDimensions(pixm, &wm, &hm, NULL);
        if (d == 8) {
            for (i = 0; i < h; i++) {
                if (i >= hm)
                    break;
                line = data + i * wpl;
                linem = datam + i * wplm;
                for (j = 0; j < w; j++) {
                    if (j >= wm)
                        break;
                    if (GET_DATA_BIT(linem, j) == 0)
                        continue;
                    sval8 = GET_DATA_BYTE(line, j);
                    dval8 = tab[sval8];
                    SET_DATA_BYTE(line, j, dval8);
                }
            }
        } else {  /* d == 32 */
            for (i = 0; i < h; i++) {
                if (i >= hm)
                    break;
                line = data + i * wpl;
                linem = datam + i * wplm;
                for (j = 0; j < w; j++) {
                    if (j >= wm)
                        break;
                    if (GET_DATA_BIT(linem, j) == 0)
                        continue;
                    sval32 = *(line + j);
                    dval32 =
                        tab[(sval32 >> L_RED_SHIFT) & 0xff] << L_RED_SHIFT |
                        tab[(sval32 >> L_GREEN_SHIFT) & 0xff] << L_GREEN_SHIFT |
                        tab[(sval32 >> L_BLUE_SHIFT) & 0xff] << L_BLUE_SHIFT;
                    *(line + j) = dval32;
                }
            }
        }
    }

    LEPT_FREE(tab);
    return 0;
}


/*!
 * \brief   pixTRCMapGeneral()
 *
 * \param[in]    pixs             32 bpp rgb; not colormapped
 * \param[in]    pixm             [optional] 1 bpp mask
 * \param[in]    nar, nag, nab    mapping arrays
 * \return  0 if OK, 1 on error
 *
 * <pre>
 * Notes:
 *      (1) This operation is in-place on %pixs.
 *      (2) Each of the r,g,b mapping arrays is of size 256. They map the
 *          input value for that color component into values in the
 *          range [0, 255].
 *      (3) In the special case where the r, g and b mapping arrays are
 *          all the same, call pixTRCMap() instead.
 *      (4) If defined, the optional 1 bpp mask %pixm has its origin
 *          aligned with %pixs, and the map function is applied only
 *          to pixels in %pixs under the fg of pixm.
 *      (5) The alpha channel is not saved.
 * </pre>
 */
l_int32
pixTRCMapGeneral(PIX   *pixs,
                 PIX   *pixm,
                 NUMA  *nar,
                 NUMA  *nag,
                 NUMA  *nab)
{
l_int32    w, h, wm, hm, wpl, wplm, i, j;
l_uint32   sval32, dval32;
l_uint32  *data, *datam, *line, *linem, *tabr, *tabg, *tabb;

    PROCNAME("pixTRCMapGeneral");

    if (!pixs || pixGetDepth(pixs) != 32)
        return ERROR_INT("pixs not defined or not 32 bpp", procName, 1);
    if (pixm && pixGetDepth(pixm) != 1)
        return ERROR_INT("pixm defined and not 1 bpp", procName, 1);
    if (!nar || !nag || !nab)
        return ERROR_INT("na{r,g,b} not all defined", procName, 1);
    if (numaGetCount(nar) != 256 || numaGetCount(nag) != 256 ||
        numaGetCount(nab) != 256)
        return ERROR_INT("na{r,g,b} not all of size 256", procName, 1);

        /* Get the arrays for efficiency */
    tabr = (l_uint32 *)numaGetIArray(nar);
    tabg = (l_uint32 *)numaGetIArray(nag);
    tabb = (l_uint32 *)numaGetIArray(nab);
    pixGetDimensions(pixs, &w, &h, NULL);
    wpl = pixGetWpl(pixs);
    data = pixGetData(pixs);
    if (!pixm) {
        for (i = 0; i < h; i++) {
            line = data + i * wpl;
            for (j = 0; j < w; j++) {
                sval32 = *(line + j);
                dval32 =
                    tabr[(sval32 >> L_RED_SHIFT) & 0xff] << L_RED_SHIFT |
                    tabg[(sval32 >> L_GREEN_SHIFT) & 0xff] << L_GREEN_SHIFT |
                    tabb[(sval32 >> L_BLUE_SHIFT) & 0xff] << L_BLUE_SHIFT;
                *(line + j) = dval32;
            }
        }
    } else {
        datam = pixGetData(pixm);
        wplm = pixGetWpl(pixm);
        pixGetDimensions(pixm, &wm, &hm, NULL);
        for (i = 0; i < h; i++) {
            if (i >= hm)
                break;
            line = data + i * wpl;
            linem = datam + i * wplm;
            for (j = 0; j < w; j++) {
                if (j >= wm)
                    break;
                if (GET_DATA_BIT(linem, j) == 0)
                    continue;
                sval32 = *(line + j);
                dval32 =
                    tabr[(sval32 >> L_RED_SHIFT) & 0xff] << L_RED_SHIFT |
                    tabg[(sval32 >> L_GREEN_SHIFT) & 0xff] << L_GREEN_SHIFT |
                    tabb[(sval32 >> L_BLUE_SHIFT) & 0xff] << L_BLUE_SHIFT;
                *(line + j) = dval32;
            }
        }
    }

    LEPT_FREE(tabr);
    LEPT_FREE(tabg);
    LEPT_FREE(tabb);
    return 0;
}



/*-----------------------------------------------------------------------*
 *                             Unsharp masking                           *
 *-----------------------------------------------------------------------*/
/*!
 * \brief   pixUnsharpMasking()
 *
 * \param[in]    pixs       all depths except 1 bpp; with or without colormaps
 * \param[in]    halfwidth  "half-width" of smoothing filter
 * \param[in]    fract      fraction of edge added back into image
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) We use symmetric smoothing filters of odd dimension,
 *          typically use sizes of 3, 5, 7, etc.  The %halfwidth parameter
 *          for these is (size - 1)/2; i.e., 1, 2, 3, etc.
 *      (2) The fract parameter is typically taken in the
 *          range:  0.2 < fract < 0.7
 *      (3) Returns a clone if no sharpening is requested.
 * </pre>
 */
PIX *
pixUnsharpMasking(PIX       *pixs,
                  l_int32    halfwidth,
                  l_float32  fract)
{
l_int32  d;
PIX     *pix1, *pixd, *pixr, *pixrs, *pixg, *pixgs, *pixb, *pixbs;

    PROCNAME("pixUnsharpMasking");

    if (!pixs || (pixGetDepth(pixs) == 1))
        return (PIX *)ERROR_PTR("pixs not defined or 1 bpp", procName, NULL);
    if (fract <= 0.0 || halfwidth <= 0) {
        L_WARNING("no sharpening requested; clone returned\n", procName);
        return pixClone(pixs);
    }

    if (halfwidth == 1 || halfwidth == 2)
        return pixUnsharpMaskingFast(pixs, halfwidth, fract, L_BOTH_DIRECTIONS);

        /* Remove colormap; clone if possible; result is either 8 or 32 bpp */
    if ((pix1 = pixConvertTo8Or32(pixs, L_CLONE, 0)) == NULL)
        return (PIX *)ERROR_PTR("pix1 not made", procName, NULL);

        /* Sharpen */
    d = pixGetDepth(pix1);
    if (d == 8) {
        pixd = pixUnsharpMaskingGray(pix1, halfwidth, fract);
    } else {  /* d == 32 */
        pixr = pixGetRGBComponent(pix1, COLOR_RED);
        pixrs = pixUnsharpMaskingGray(pixr, halfwidth, fract);
        pixDestroy(&pixr);
        pixg = pixGetRGBComponent(pix1, COLOR_GREEN);
        pixgs = pixUnsharpMaskingGray(pixg, halfwidth, fract);
        pixDestroy(&pixg);
        pixb = pixGetRGBComponent(pix1, COLOR_BLUE);
        pixbs = pixUnsharpMaskingGray(pixb, halfwidth, fract);
        pixDestroy(&pixb);
        pixd = pixCreateRGBImage(pixrs, pixgs, pixbs);
        pixDestroy(&pixrs);
        pixDestroy(&pixgs);
        pixDestroy(&pixbs);
        if (pixGetSpp(pixs) == 4)
            pixCopyRGBComponent(pixd, pixs, L_ALPHA_CHANNEL);
    }

    pixDestroy(&pix1);
    return pixd;
}


/*!
 * \brief   pixUnsharpMaskingGray()
 *
 * \param[in]    pixs       8 bpp; no colormap
 * \param[in]    halfwidth  "half-width" of smoothing filter
 * \param[in]    fract      fraction of edge added back into image
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) We use symmetric smoothing filters of odd dimension,
 *          typically use sizes of 3, 5, 7, etc.  The %halfwidth parameter
 *          for these is (size - 1)/2; i.e., 1, 2, 3, etc.
 *      (2) The fract parameter is typically taken in the range:
 *          0.2 < fract < 0.7
 *      (3) Returns a clone if no sharpening is requested.
 * </pre>
 */
PIX *
pixUnsharpMaskingGray(PIX       *pixs,
                      l_int32    halfwidth,
                      l_float32  fract)
{
l_int32  w, h, d;
PIX     *pixc, *pixd;
PIXACC  *pixacc;

    PROCNAME("pixUnsharpMaskingGray");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 8 || pixGetColormap(pixs) != NULL)
        return (PIX *)ERROR_PTR("pixs not 8 bpp or has cmap", procName, NULL);
    if (fract <= 0.0 || halfwidth <= 0) {
        L_WARNING("no sharpening requested; clone returned\n", procName);
        return pixClone(pixs);
    }
    if (halfwidth == 1 || halfwidth == 2)
        return pixUnsharpMaskingGrayFast(pixs, halfwidth, fract,
                                         L_BOTH_DIRECTIONS);

    if ((pixc = pixBlockconvGray(pixs, NULL, halfwidth, halfwidth)) == NULL)
        return (PIX *)ERROR_PTR("pixc not made", procName, NULL);

        /* Steps:
         *    (1) edge image is pixs - pixc  (this is highpass part)
         *    (2) multiply edge image by fract
         *    (3) add fraction of edge to pixs
         *
         * To show how this is done with both interfaces to arithmetic
         * on integer Pix, here is the implementation in the lower-level
         * function calls:
         *    pixt = pixInitAccumulate(w, h, 0x10000000)) == NULL)
         *    pixAccumulate(pixt, pixs, L_ARITH_ADD);
         *    pixAccumulate(pixt, pixc, L_ARITH_SUBTRACT);
         *    pixMultConstAccumulate(pixt, fract, 0x10000000);
         *    pixAccumulate(pixt, pixs, L_ARITH_ADD);
         *    pixd = pixFinalAccumulate(pixt, 0x10000000, 8)) == NULL)
         *    pixDestroy(&pixt);
         *
         * The code below does the same thing using the Pixacc accumulator,
         * hiding the details of the offset that is needed for subtraction.
         */
    pixacc = pixaccCreate(w, h, 1);
    pixaccAdd(pixacc, pixs);
    pixaccSubtract(pixacc, pixc);
    pixaccMultConst(pixacc, fract);
    pixaccAdd(pixacc, pixs);
    pixd = pixaccFinal(pixacc, 8);
    pixaccDestroy(&pixacc);

    pixDestroy(&pixc);
    return pixd;
}


/*!
 * \brief   pixUnsharpMaskingFast()
 *
 * \param[in]    pixs       all depths except 1 bpp; with or without colormaps
 * \param[in]    halfwidth  "half-width" of smoothing filter; 1 and 2 only
 * \param[in]    fract      fraction of high frequency added to image
 * \param[in]    direction  L_HORIZ, L_VERT, L_BOTH_DIRECTIONS
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) The fast version uses separable 1-D filters directly on
 *          the input image.  The halfwidth is either 1 (full width = 3)
 *          or 2 (full width = 5).
 *      (2) The fract parameter is typically taken in the
 *            range:  0.2 < fract < 0.7
 *      (3) To skip horizontal sharpening, use %fracth = 0.0; ditto for %fractv
 *      (4) For one dimensional filtering (as an example):
 *          For %halfwidth = 1, the low-pass filter is
 *              L:    1/3    1/3   1/3
 *          and the high-pass filter is
 *              H = I - L:   -1/3   2/3   -1/3
 *          For %halfwidth = 2, the low-pass filter is
 *              L:    1/5    1/5   1/5    1/5    1/5
 *          and the high-pass filter is
 *              H = I - L:   -1/5  -1/5   4/5  -1/5   -1/5
 *          The new sharpened pixel value is found by adding some fraction
 *          of the high-pass filter value (which sums to 0) to the
 *          initial pixel value:
 *              N = I + fract * H
 *      (5) For 2D, the sharpening filter is not separable, because the
 *          vertical filter depends on the horizontal location relative
 *          to the filter origin, and v.v.   So we either do the full
 *          2D filter (for %halfwidth == 1) or do the low-pass
 *          convolution separably and then compose with the original pix.
 *      (6) Returns a clone if no sharpening is requested.
 * </pre>
 */
PIX *
pixUnsharpMaskingFast(PIX       *pixs,
                      l_int32    halfwidth,
                      l_float32  fract,
                      l_int32    direction)
{
l_int32  d;
PIX     *pixt, *pixd, *pixr, *pixrs, *pixg, *pixgs, *pixb, *pixbs;

    PROCNAME("pixUnsharpMaskingFast");

    if (!pixs || (pixGetDepth(pixs) == 1))
        return (PIX *)ERROR_PTR("pixs not defined or 1 bpp", procName, NULL);
    if (fract <= 0.0 || halfwidth <= 0) {
        L_WARNING("no sharpening requested; clone returned\n", procName);
        return pixClone(pixs);
    }
    if (halfwidth != 1 && halfwidth != 2)
        return (PIX *)ERROR_PTR("halfwidth must be 1 or 2", procName, NULL);
    if (direction != L_HORIZ && direction != L_VERT &&
        direction != L_BOTH_DIRECTIONS)
        return (PIX *)ERROR_PTR("invalid direction", procName, NULL);

        /* Remove colormap; clone if possible; result is either 8 or 32 bpp */
    if ((pixt = pixConvertTo8Or32(pixs, L_CLONE, 0)) == NULL)
        return (PIX *)ERROR_PTR("pixt not made", procName, NULL);

        /* Sharpen */
    d = pixGetDepth(pixt);
    if (d == 8) {
        pixd = pixUnsharpMaskingGrayFast(pixt, halfwidth, fract, direction);
    } else {  /* d == 32 */
        pixr = pixGetRGBComponent(pixs, COLOR_RED);
        pixrs = pixUnsharpMaskingGrayFast(pixr, halfwidth, fract, direction);
        pixDestroy(&pixr);
        pixg = pixGetRGBComponent(pixs, COLOR_GREEN);
        pixgs = pixUnsharpMaskingGrayFast(pixg, halfwidth, fract, direction);
        pixDestroy(&pixg);
        pixb = pixGetRGBComponent(pixs, COLOR_BLUE);
        pixbs = pixUnsharpMaskingGrayFast(pixb, halfwidth, fract, direction);
        pixDestroy(&pixb);
        pixd = pixCreateRGBImage(pixrs, pixgs, pixbs);
        if (pixGetSpp(pixs) == 4)
            pixCopyRGBComponent(pixd, pixs, L_ALPHA_CHANNEL);
        pixDestroy(&pixrs);
        pixDestroy(&pixgs);
        pixDestroy(&pixbs);
    }

    pixDestroy(&pixt);
    return pixd;
}



/*!
 * \brief   pixUnsharpMaskingGrayFast()
 *
 * \param[in]    pixs       8 bpp; no colormap
 * \param[in]    halfwidth  "half-width" of smoothing filter: 1 or 2
 * \param[in]    fract      fraction of high frequency added to image
 * \param[in]    direction  L_HORIZ, L_VERT, L_BOTH_DIRECTIONS
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) For usage and explanation of the algorithm, see notes
 *          in pixUnsharpMaskingFast().
 *      (2) Returns a clone if no sharpening is requested.
 * </pre>
 */
PIX *
pixUnsharpMaskingGrayFast(PIX       *pixs,
                          l_int32    halfwidth,
                          l_float32  fract,
                          l_int32    direction)
{
PIX  *pixd;

    PROCNAME("pixUnsharpMaskingGrayFast");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (pixGetDepth(pixs) != 8 || pixGetColormap(pixs) != NULL)
        return (PIX *)ERROR_PTR("pixs not 8 bpp or has cmap", procName, NULL);
    if (fract <= 0.0 || halfwidth <= 0) {
        L_WARNING("no sharpening requested; clone returned\n", procName);
        return pixClone(pixs);
    }
    if (halfwidth != 1 && halfwidth != 2)
        return (PIX *)ERROR_PTR("halfwidth must be 1 or 2", procName, NULL);
    if (direction != L_HORIZ && direction != L_VERT &&
        direction != L_BOTH_DIRECTIONS)
        return (PIX *)ERROR_PTR("invalid direction", procName, NULL);

    if (direction != L_BOTH_DIRECTIONS)
        pixd = pixUnsharpMaskingGray1D(pixs, halfwidth, fract, direction);
    else  /* 2D sharpening */
        pixd = pixUnsharpMaskingGray2D(pixs, halfwidth, fract);

    return pixd;
}


/*!
 * \brief   pixUnsharpMaskingGray1D()
 *
 * \param[in]    pixs        8 bpp; no colormap
 * \param[in]    halfwidth   "half-width" of smoothing filter: 1 or 2
 * \param[in]    fract       fraction of high frequency added to image
 * \param[in]    direction   filtering direction; use L_HORIZ or L_VERT
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) For usage and explanation of the algorithm, see notes
 *          in pixUnsharpMaskingFast().
 *      (2) Returns a clone if no sharpening is requested.
 * </pre>
 */
PIX *
pixUnsharpMaskingGray1D(PIX       *pixs,
                        l_int32    halfwidth,
                        l_float32  fract,
                        l_int32    direction)
{
l_int32    w, h, d, wpls, wpld, i, j, ival;
l_uint32  *datas, *datad;
l_uint32  *lines, *lines0, *lines1, *lines2, *lines3, *lines4, *lined;
l_float32  val, a[5];
PIX       *pixd;

    PROCNAME("pixUnsharpMaskingGray1D");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 8 || pixGetColormap(pixs) != NULL)
        return (PIX *)ERROR_PTR("pixs not 8 bpp or has cmap", procName, NULL);
    if (fract <= 0.0 || halfwidth <= 0) {
        L_WARNING("no sharpening requested; clone returned\n", procName);
        return pixClone(pixs);
    }
    if (halfwidth != 1 && halfwidth != 2)
        return (PIX *)ERROR_PTR("halfwidth must be 1 or 2", procName, NULL);

        /* Initialize pixd with pixels from pixs that will not be
         * set when computing the sharpened values. */
    pixd = pixCopyBorder(NULL, pixs, halfwidth, halfwidth,
                         halfwidth, halfwidth);
    datas = pixGetData(pixs);
    datad = pixGetData(pixd);
    wpls = pixGetWpl(pixs);
    wpld = pixGetWpl(pixd);

    if (halfwidth == 1) {
        a[0] = -fract / 3.0;
        a[1] = 1.0 + fract * 2.0 / 3.0;
        a[2] = a[0];
    } else {  /* halfwidth == 2 */
        a[0] = -fract / 5.0;
        a[1] = a[0];
        a[2] = 1.0 + fract * 4.0 / 5.0;
        a[3] = a[0];
        a[4] = a[0];
    }

    if (direction == L_HORIZ) {
        for (i = 0; i < h; i++) {
            lines = datas + i * wpls;
            lined = datad + i * wpld;
            if (halfwidth == 1) {
                for (j = 1; j < w - 1; j++) {
                    val = a[0] * GET_DATA_BYTE(lines, j - 1) +
                          a[1] * GET_DATA_BYTE(lines, j) +
                          a[2] * GET_DATA_BYTE(lines, j + 1);
                    ival = (l_int32)val;
                    ival = L_MAX(0, ival);
                    ival = L_MIN(255, ival);
                    SET_DATA_BYTE(lined, j, ival);
                }
            } else {  /* halfwidth == 2 */
                for (j = 2; j < w - 2; j++) {
                    val = a[0] * GET_DATA_BYTE(lines, j - 2) +
                          a[1] * GET_DATA_BYTE(lines, j - 1) +
                          a[2] * GET_DATA_BYTE(lines, j) +
                          a[3] * GET_DATA_BYTE(lines, j + 1) +
                          a[4] * GET_DATA_BYTE(lines, j + 2);
                    ival = (l_int32)val;
                    ival = L_MAX(0, ival);
                    ival = L_MIN(255, ival);
                    SET_DATA_BYTE(lined, j, ival);
                }
            }
        }
    } else {  /* direction == L_VERT */
        if (halfwidth == 1) {
            for (i = 1; i < h - 1; i++) {
                lines0 = datas + (i - 1) * wpls;
                lines1 = datas + i * wpls;
                lines2 = datas + (i + 1) * wpls;
                lined = datad + i * wpld;
                for (j = 0; j < w; j++) {
                    val = a[0] * GET_DATA_BYTE(lines0, j) +
                          a[1] * GET_DATA_BYTE(lines1, j) +
                          a[2] * GET_DATA_BYTE(lines2, j);
                    ival = (l_int32)val;
                    ival = L_MAX(0, ival);
                    ival = L_MIN(255, ival);
                    SET_DATA_BYTE(lined, j, ival);
                }
            }
        } else {  /* halfwidth == 2 */
            for (i = 2; i < h - 2; i++) {
                lines0 = datas + (i - 2) * wpls;
                lines1 = datas + (i - 1) * wpls;
                lines2 = datas + i * wpls;
                lines3 = datas + (i + 1) * wpls;
                lines4 = datas + (i + 2) * wpls;
                lined = datad + i * wpld;
                for (j = 0; j < w; j++) {
                    val = a[0] * GET_DATA_BYTE(lines0, j) +
                          a[1] * GET_DATA_BYTE(lines1, j) +
                          a[2] * GET_DATA_BYTE(lines2, j) +
                          a[3] * GET_DATA_BYTE(lines3, j) +
                          a[4] * GET_DATA_BYTE(lines4, j);
                    ival = (l_int32)val;
                    ival = L_MAX(0, ival);
                    ival = L_MIN(255, ival);
                    SET_DATA_BYTE(lined, j, ival);
                }
            }
        }
    }

    return pixd;
}


/*!
 * \brief   pixUnsharpMaskingGray2D()
 *
 * \param[in]    pixs       8 bpp; no colormap
 * \param[in]    halfwidth  "half-width" of smoothing filter: 1 or 2
 * \param[in]    fract      fraction of high frequency added to image
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) This is for %halfwidth == 1, 2.
 *      (2) The lowpass filter is implemented separably.
 *      (3) Returns a clone if no sharpening is requested.
 * </pre>
 */
PIX *
pixUnsharpMaskingGray2D(PIX       *pixs,
                        l_int32    halfwidth,
                        l_float32  fract)
{
l_int32     w, h, d, wpls, wpld, wplf, i, j, ival, sval;
l_uint32   *datas, *datad, *lines, *lined;
l_float32   val, norm;
l_float32  *dataf, *linef, *linef0, *linef1, *linef2, *linef3, *linef4;
PIX        *pixd;
FPIX       *fpix;

    PROCNAME("pixUnsharpMaskingGray2D");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 8 || pixGetColormap(pixs) != NULL)
        return (PIX *)ERROR_PTR("pixs not 8 bpp or has cmap", procName, NULL);
    if (fract <= 0.0 || halfwidth <= 0) {
        L_WARNING("no sharpening requested; clone returned\n", procName);
        return pixClone(pixs);
    }
    if (halfwidth != 1 && halfwidth != 2)
        return (PIX *)ERROR_PTR("halfwidth must be 1 or 2", procName, NULL);

    if ((pixd = pixCopyBorder(NULL, pixs, halfwidth, halfwidth,
                              halfwidth, halfwidth)) == NULL)
        return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
    datad = pixGetData(pixd);
    wpld = pixGetWpl(pixd);
    datas = pixGetData(pixs);
    wpls = pixGetWpl(pixs);

        /* Do the low pass separably.  Store the result of horizontal
         * smoothing in an intermediate fpix.  */
    if ((fpix = fpixCreate(w, h)) == NULL) {
        pixDestroy(&pixd);
        return (PIX *)ERROR_PTR("fpix not made", procName, NULL);
    }
    dataf = fpixGetData(fpix);
    wplf = fpixGetWpl(fpix);
    if (halfwidth == 1) {
        for (i = 0; i < h; i++) {
            lines = datas + i * wpls;
            linef = dataf + i * wplf;
            for (j = 1; j < w - 1; j++) {
                val = GET_DATA_BYTE(lines, j - 1) +
                      GET_DATA_BYTE(lines, j) +
                      GET_DATA_BYTE(lines, j + 1);
                linef[j] = val;
            }
        }
    } else {
        for (i = 0; i < h; i++) {
            lines = datas + i * wpls;
            linef = dataf + i * wplf;
            for (j = 2; j < w - 2; j++) {
                val = GET_DATA_BYTE(lines, j - 2) +
                      GET_DATA_BYTE(lines, j - 1) +
                      GET_DATA_BYTE(lines, j) +
                      GET_DATA_BYTE(lines, j + 1) +
                      GET_DATA_BYTE(lines, j + 2);
                linef[j] = val;
            }
        }
    }

        /* Do vertical smoothing to finish the low-pass filter.
         * At each pixel, if L is the lowpass value, I is the
         * src pixel value and f is the fraction of highpass to
         * be added to I, then the highpass filter value is
         *     H = I - L
         * and the new sharpened value is
         *     N = I + f * H.                 */
    if (halfwidth == 1) {
        for (i = 1; i < h - 1; i++) {
            linef0 = dataf + (i - 1) * wplf;
            linef1 = dataf + i * wplf;
            linef2 = dataf + (i + 1) * wplf;
            lined = datad + i * wpld;
            lines = datas + i * wpls;
            norm = 1.0 / 9.0;
            for (j = 1; j < w - 1; j++) {
                val = norm * (linef0[j] + linef1[j] +
                              linef2[j]);         /* L: lowpass filter value */
                sval = GET_DATA_BYTE(lines, j);   /* I: source pixel */
                ival = (l_int32)(sval + fract * (sval - val) + 0.5);
                ival = L_MAX(0, ival);
                ival = L_MIN(255, ival);
                SET_DATA_BYTE(lined, j, ival);
            }
        }
    } else {
        for (i = 2; i < h - 2; i++) {
            linef0 = dataf + (i - 2) * wplf;
            linef1 = dataf + (i - 1) * wplf;
            linef2 = dataf + i * wplf;
            linef3 = dataf + (i + 1) * wplf;
            linef4 = dataf + (i + 2) * wplf;
            lined = datad + i * wpld;
            lines = datas + i * wpls;
            norm = 1.0 / 25.0;
            for (j = 2; j < w - 2; j++) {
                val = norm * (linef0[j] + linef1[j] + linef2[j] + linef3[j] +
                              linef4[j]);  /* L: lowpass filter value */
                sval = GET_DATA_BYTE(lines, j);   /* I: source pixel */
                ival = (l_int32)(sval + fract * (sval - val) + 0.5);
                ival = L_MAX(0, ival);
                ival = L_MIN(255, ival);
                SET_DATA_BYTE(lined, j, ival);
            }
        }
    }

    fpixDestroy(&fpix);
    return pixd;
}


/*-----------------------------------------------------------------------*
 *                    Hue and saturation modification                    *
 *-----------------------------------------------------------------------*/
/*!
 * \brief   pixModifyHue()
 *
 * \param[in]    pixd      [optional] can be null or equal to pixs
 * \param[in]    pixs      32 bpp rgb
 * \param[in]    fract     between -1.0 and 1.0
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) pixd must either be null or equal to pixs.
 *          For in-place operation, set pixd == pixs:
 *             pixEqualizeTRC(pixs, pixs, ...);
 *          To get a new image, set pixd == null:
 *             pixd = pixEqualizeTRC(NULL, pixs, ...);
 *      (2) Use fract > 0.0 to increase hue value; < 0.0 to decrease it.
 *          1.0 (or -1.0) represents a 360 degree rotation; i.e., no change.
 *      (3) If no modification is requested (fract = -1.0 or 0 or 1.0),
 *          return a copy unless in-place, in which case this is a no-op.
 *      (4) This leaves saturation and intensity invariant.
 *      (5) See discussion of color-modification methods, in coloring.c.
 * </pre>
 */
PIX  *
pixModifyHue(PIX       *pixd,
             PIX       *pixs,
             l_float32  fract)
{
l_int32    w, h, d, i, j, wpl, delhue;
l_int32    rval, gval, bval, hval, sval, vval;
l_uint32  *data, *line;

    PROCNAME("pixModifyHue");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (pixGetColormap(pixs) != NULL)
        return (PIX *)ERROR_PTR("pixs colormapped", procName, NULL);
    if (pixd && (pixd != pixs))
        return (PIX *)ERROR_PTR("pixd not null or pixs", procName, pixd);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 32)
        return (PIX *)ERROR_PTR("pixs not 32 bpp", procName, NULL);
    if (L_ABS(fract) > 1.0)
        return (PIX *)ERROR_PTR("fract not in [-1.0 ... 1.0]", procName, NULL);

    pixd = pixCopy(pixd, pixs);

    delhue = (l_int32)(240 * fract);
    if (delhue == 0 || delhue == 240 || delhue == -240) {
        L_WARNING("no change requested in hue\n", procName);
        return pixd;
    }
    if (delhue < 0)
        delhue += 240;

    data = pixGetData(pixd);
    wpl = pixGetWpl(pixd);
    for (i = 0; i < h; i++) {
        line = data + i * wpl;
        for (j = 0; j < w; j++) {
            extractRGBValues(line[j], &rval, &gval, &bval);
            convertRGBToHSV(rval, gval, bval, &hval, &sval, &vval);
            hval = (hval + delhue) % 240;
            convertHSVToRGB(hval, sval, vval, &rval, &gval, &bval);
            composeRGBPixel(rval, gval, bval, line + j);
        }
    }
    if (pixGetSpp(pixs) == 4)
        pixCopyRGBComponent(pixd, pixs, L_ALPHA_CHANNEL);

    return pixd;
}


/*!
 * \brief   pixModifySaturation()
 *
 * \param[in]    pixd     [optional] can be null, existing or equal to pixs
 * \param[in]    pixs     32 bpp rgb
 * \param[in]    fract    between -1.0 and 1.0
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) If fract > 0.0, it gives the fraction that the pixel
 *          saturation is moved from its initial value toward 255.
 *          If fract < 0.0, it gives the fraction that the pixel
 *          saturation is moved from its initial value toward 0.
 *          The limiting values for fract = -1.0 (1.0) thus set the
 *          saturation to 0 (255).
 *      (2) If fract = 0, no modification is requested; return a copy
 *          unless in-place, in which case this is a no-op.
 *      (3) This leaves hue and intensity invariant.
 *      (4) See discussion of color-modification methods, in coloring.c.
 * </pre>
 */
PIX  *
pixModifySaturation(PIX       *pixd,
                    PIX       *pixs,
                    l_float32  fract)
{
l_int32    w, h, d, i, j, wpl;
l_int32    rval, gval, bval, hval, sval, vval;
l_uint32  *data, *line;

    PROCNAME("pixModifySaturation");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 32)
        return (PIX *)ERROR_PTR("pixs not 32 bpp", procName, NULL);
    if (L_ABS(fract) > 1.0)
        return (PIX *)ERROR_PTR("fract not in [-1.0 ... 1.0]", procName, NULL);

    pixd = pixCopy(pixd, pixs);
    if (fract == 0.0) {
        L_WARNING("no change requested in saturation\n", procName);
        return pixd;
    }

    data = pixGetData(pixd);
    wpl = pixGetWpl(pixd);
    for (i = 0; i < h; i++) {
        line = data + i * wpl;
        for (j = 0; j < w; j++) {
            extractRGBValues(line[j], &rval, &gval, &bval);
            convertRGBToHSV(rval, gval, bval, &hval, &sval, &vval);
            if (fract < 0.0)
                sval = (l_int32)(sval * (1.0 + fract));
            else
                sval = (l_int32)(sval + fract * (255 - sval));
            convertHSVToRGB(hval, sval, vval, &rval, &gval, &bval);
            composeRGBPixel(rval, gval, bval, line + j);
        }
    }
    if (pixGetSpp(pixs) == 4)
        pixCopyRGBComponent(pixd, pixs, L_ALPHA_CHANNEL);

    return pixd;
}


/*!
 * \brief   pixMeasureSaturation()
 *
 * \param[in]    pixs     32 bpp rgb
 * \param[in]    factor   subsampling factor; integer >= 1
 * \param[out]   psat     average saturation
 * \return  0 if OK, 1 on error
 */
l_int32
pixMeasureSaturation(PIX        *pixs,
                     l_int32     factor,
                     l_float32  *psat)
{
l_int32    w, h, d, i, j, wpl, sum, count;
l_int32    rval, gval, bval, hval, sval, vval;
l_uint32  *data, *line;

    PROCNAME("pixMeasureSaturation");

    if (!psat)
        return ERROR_INT("pixs not defined", procName, 1);
    *psat = 0.0;
    if (!pixs)
        return ERROR_INT("pixs not defined", procName, 1);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 32)
        return ERROR_INT("pixs not 32 bpp", procName, 1);
    if (factor < 1)
        return ERROR_INT("subsampling factor < 1", procName, 1);

    data = pixGetData(pixs);
    wpl = pixGetWpl(pixs);
    for (i = 0, sum = 0, count = 0; i < h; i += factor) {
        line = data + i * wpl;
        for (j = 0; j < w; j += factor) {
            extractRGBValues(line[j], &rval, &gval, &bval);
            convertRGBToHSV(rval, gval, bval, &hval, &sval, &vval);
            sum += sval;
            count++;
        }
    }

    if (count > 0)
        *psat = (l_float32)sum / (l_float32)count;
    return 0;
}


/*!
 * \brief   pixModifyBrightness()
 *
 * \param[in]    pixd     [optional] can be null, existing or equal to pixs
 * \param[in]    pixs     32 bpp rgb
 * \param[in]    fract    between -1.0 and 1.0
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) If fract > 0.0, it gives the fraction that the v-parameter,
 *          which is max(r,g,b), is moved from its initial value toward 255.
 *          If fract < 0.0, it gives the fraction that the v-parameter
 *          is moved from its initial value toward 0.
 *          The limiting values for fract = -1.0 (1.0) thus set the
 *          v-parameter to 0 (255).
 *      (2) If fract = 0, no modification is requested; return a copy
 *          unless in-place, in which case this is a no-op.
 *      (3) This leaves hue and saturation invariant.
 *      (4) See discussion of color-modification methods, in coloring.c.
 * </pre>
 */
PIX  *
pixModifyBrightness(PIX       *pixd,
                    PIX       *pixs,
                    l_float32  fract)
{
l_int32    w, h, d, i, j, wpl;
l_int32    rval, gval, bval, hval, sval, vval;
l_uint32  *data, *line;

    PROCNAME("pixModifyBrightness");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 32)
        return (PIX *)ERROR_PTR("pixs not 32 bpp", procName, NULL);
    if (L_ABS(fract) > 1.0)
        return (PIX *)ERROR_PTR("fract not in [-1.0 ... 1.0]", procName, NULL);

    pixd = pixCopy(pixd, pixs);
    if (fract == 0.0) {
        L_WARNING("no change requested in brightness\n", procName);
        return pixd;
    }

    data = pixGetData(pixd);
    wpl = pixGetWpl(pixd);
    for (i = 0; i < h; i++) {
        line = data + i * wpl;
        for (j = 0; j < w; j++) {
            extractRGBValues(line[j], &rval, &gval, &bval);
            convertRGBToHSV(rval, gval, bval, &hval, &sval, &vval);
            if (fract > 0.0)
                vval = (l_int32)(vval + fract * (255.0 - vval));
            else
                vval = (l_int32)(vval * (1.0 + fract));
            convertHSVToRGB(hval, sval, vval, &rval, &gval, &bval);
            composeRGBPixel(rval, gval, bval, line + j);
        }
    }
    if (pixGetSpp(pixs) == 4)
        pixCopyRGBComponent(pixd, pixs, L_ALPHA_CHANNEL);

    return pixd;
}


/*-----------------------------------------------------------------------*
 *                             Color shifting                            *
 *-----------------------------------------------------------------------*/
/*!
 * \brief   pixMosaicColorShiftRGB()
 *
 * \param[in]    pixs     32 bpp rgb
 * \param[in]    roff   center offset of red component
 * \param[in]    goff   center offset of green component
 * \param[in]    boff   center offset of blue component
 * \param[in]    delta  increments from center offsets [0.0 - 0.1];
 *                      use 0.0 to get the default (0.04)
 * \param[in]    nincr  number of increments in each (positive and negative)
 *                      direction; use 0 to get the default (2).
 * \return  pix, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) This generates a mosaic view of the effect of shifting the RGB
 *          components.  See pixColorShiftRGB() for details on the shifting.
 *      (2) The offsets (%roff, %goff, %boff) set the color center point,
 *          and the deviations from this are shown separately for deltas
 *          in r, g and b.  For each component, we show 2 * %nincr + 1
 *          images.
 *      (3) The pix must have minimum dimensions of 100 and an aspect
 *          ratio not exceeding 5.0.
 *      (4) Usage: color prints differ from the original due to three factors:
 *          illumination, calibration of the camera in acquisition,
 *          and calibration of the printer.  This function can be used
 *          to iteratively match a color print to the original.  On each
 *          iteration, the center offsets are set to the best match so
 *          far, and the %delta increments are typically reduced.
 * </pre>
 */
PIX *
pixMosaicColorShiftRGB(PIX       *pixs,
                       l_float32  roff,
                       l_float32  goff,
                       l_float32  boff,
                       l_float32  delta,
                       l_int32    nincr)
{
char       buf[64];
l_int32    i, w, h;
l_float32  del, ratio;
L_BMF     *bmf;
PIX       *pix1, *pix2, *pix3;
PIXA      *pixa;

    PROCNAME("pixMosaicColorShiftRGB");

    if (!pixs  || pixGetDepth(pixs) != 32)
        return (PIX *)ERROR_PTR("pixs undefined or not rgb", procName, NULL);
    if (roff < -1.0 || roff > 1.0)
        return (PIX *)ERROR_PTR("roff not in [-1.0, 1.0]", procName, NULL);
    if (goff < -1.0 || goff > 1.0)
        return (PIX *)ERROR_PTR("goff not in [-1.0, 1.0]", procName, NULL);
    if (boff < -1.0 || boff > 1.0)
        return (PIX *)ERROR_PTR("boff not in [-1.0, 1.0]", procName, NULL);
    if (delta < 0.0 || delta > 0.1)
        return (PIX *)ERROR_PTR("delta not in [0.0, 0.1]", procName, NULL);
    if (delta == 0.0) delta = 0.04;
    if (nincr < 0 || nincr > 6)
        return (PIX *)ERROR_PTR("nincr not in [0, 6]", procName, NULL);
    if (nincr == 0) nincr = 2;

        /* Require width and height to be >= 100, and the aspect ratio <= 5.0 */
    pixGetDimensions(pixs, &w, &h, NULL);
    if (w < 100 || h < 100)
        return (PIX *)ERROR_PTR("w and h not both >= 100", procName, NULL);
    pixMaxAspectRatio(pixs, &ratio);
    if (ratio < 1.0 || ratio > 5.0) {
        L_ERROR("invalid aspect ratio %5.1f\n", procName, ratio);
        return NULL;
    }

    pixa = pixaCreate(3 * (2 * nincr + 1));
    bmf = bmfCreate(NULL, 8);
    pix1 = pixScaleToSize(pixs, 400, 0);
    for (i = 0, del = - nincr * delta; i < 2 * nincr + 1; i++, del += delta) {
        pix2 = pixColorShiftRGB(pix1, roff + del, goff, boff);
        snprintf(buf, sizeof(buf), "%4.2f, %4.2f, %4.2f",
                 roff + del, goff, boff);
        pix3 = pixAddSingleTextblock(pix2, bmf, buf, 0xff000000,
                                     L_ADD_BELOW, 0);
        pixaAddPix(pixa, pix3, L_INSERT);
        pixDestroy(&pix2);
    }
    for (i = 0, del = - nincr * delta; i < 2 * nincr + 1; i++, del += delta) {
        pix2 = pixColorShiftRGB(pix1, roff, goff + del, boff);
        snprintf(buf, sizeof(buf), "%4.2f, %4.2f, %4.2f",
                 roff, goff + del, boff);
        pix3 = pixAddSingleTextblock(pix2, bmf, buf, 0xff000000,
                                     L_ADD_BELOW, 0);
        pixaAddPix(pixa, pix3, L_INSERT);
        pixDestroy(&pix2);
    }
    for (i = 0, del = - nincr * delta; i < 2 * nincr + 1; i++, del += delta) {
        pix2 = pixColorShiftRGB(pix1, roff, goff, boff + del);
        snprintf(buf, sizeof(buf), "%4.2f, %4.2f, %4.2f",
                 roff, goff, boff + del);
        pix3 = pixAddSingleTextblock(pix2, bmf, buf, 0xff000000,
                                     L_ADD_BELOW, 0);
        pixaAddPix(pixa, pix3, L_INSERT);
        pixDestroy(&pix2);
    }
    pixDestroy(&pix1);

    pix1 = pixaDisplayTiledAndScaled(pixa, 32, 300, 2 * nincr + 1, 0, 30, 2);
    pixaDestroy(&pixa);
    bmfDestroy(&bmf);
    return pix1;
}


/*!
 * \brief   pixColorShiftRGB()
 *
 * \param[in]    pixs     32 bpp rgb
 * \param[in]    rfract   fractional shift in red component
 * \param[in]    gfract   fractional shift in green component
 * \param[in]    bfract   fractional shift in blue component
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) This allows independent fractional shifts of the r,g and b
 *          components.  A positive shift pushes to saturation (255);
 *          a negative shift pushes toward 0 (black).
 *      (2) The effect can be imagined using a color wheel that consists
 *          (for our purposes) of these 6 colors, separated by 60 degrees:
 *             red, magenta, blue, cyan, green, yellow
 *      (3) So, for example, a negative shift of the blue component
 *          (bfract < 0) could be accompanied by positive shifts
 *          of red and green to make an image more yellow.
 *      (4) Examples of limiting cases:
 *            rfract = 1 ==> r = 255
 *            rfract = -1 ==> r = 0
 * </pre>
 */
PIX *
pixColorShiftRGB(PIX       *pixs,
                 l_float32  rfract,
                 l_float32  gfract,
                 l_float32  bfract)
{
l_int32    w, h, i, j, wpls, wpld, rval, gval, bval;
l_int32   *rlut, *glut, *blut;
l_uint32  *datas, *datad, *lines, *lined;
l_float32  fi;
PIX       *pixd;

    PROCNAME("pixColorShiftRGB");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (pixGetDepth(pixs) != 32)
        return (PIX *)ERROR_PTR("pixs not 32 bpp", procName, NULL);
    if (rfract < -1.0 || rfract > 1.0)
        return (PIX *)ERROR_PTR("rfract not in [-1.0, 1.0]", procName, NULL);
    if (gfract < -1.0 || gfract > 1.0)
        return (PIX *)ERROR_PTR("gfract not in [-1.0, 1.0]", procName, NULL);
    if (bfract < -1.0 || bfract > 1.0)
        return (PIX *)ERROR_PTR("bfract not in [-1.0, 1.0]", procName, NULL);
    if (rfract == 0.0 && gfract == 0.0 && bfract == 0.0)
        return pixCopy(NULL, pixs);

    rlut = (l_int32 *)LEPT_CALLOC(256, sizeof(l_int32));
    glut = (l_int32 *)LEPT_CALLOC(256, sizeof(l_int32));
    blut = (l_int32 *)LEPT_CALLOC(256, sizeof(l_int32));
    for (i = 0; i < 256; i++) {
        fi = i;
        if (rfract >= 0) {
            rlut[i] = (l_int32)(fi + (255.0 - fi) * rfract);
        } else {
            rlut[i] = (l_int32)(fi * (1.0 + rfract));
        }
        if (gfract >= 0) {
            glut[i] = (l_int32)(fi + (255.0 - fi) * gfract);
        } else {
            glut[i] = (l_int32)(fi * (1.0 + gfract));
        }
        if (bfract >= 0) {
            blut[i] = (l_int32)(fi + (255.0 - fi) * bfract);
        } else {
            blut[i] = (l_int32)(fi * (1.0 + bfract));
        }
    }

    pixGetDimensions(pixs, &w, &h, NULL);
    datas = pixGetData(pixs);
    wpls = pixGetWpl(pixs);
    pixd = pixCreate(w, h, 32);
    datad = pixGetData(pixd);
    wpld = pixGetWpl(pixd);
    for (i = 0; i < h; i++) {
        lines = datas + i * wpls;
        lined = datad + i * wpld;
        for (j = 0; j < w; j++) {
            extractRGBValues(lines[j], &rval, &gval, &bval);
            composeRGBPixel(rlut[rval], glut[gval], blut[bval], lined + j);
        }
    }

    LEPT_FREE(rlut);
    LEPT_FREE(glut);
    LEPT_FREE(blut);
    return pixd;
}

/*-----------------------------------------------------------------------*
 *                     Darken gray (unsaturated) pixels
 *-----------------------------------------------------------------------*/
/*!
 * \brief   pixDarkenGray()
 *
 * \param[in]    pixd      [optional] can be null or equal to pixs
 * \param[in]    pixs      32 bpp rgb
 * \param[in]    thresh    pixels with max component >= %thresh are unchanged
 * \param[in]    satlimit  pixels with saturation >= %satlimit are unchanged
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) This darkens gray pixels, by a fraction (sat/%satlimit), where
 *          the saturation, sat, is the component difference (max - min).
 *          The pixel value is unchanged if sat >= %satlimit.  A typical
 *          value of %satlimit might be 40; the larger the value, the
 *          more that pixels with a smaller saturation will be darkened.
 *      (2) Pixels with max component >= %thresh are unchanged. This can be
 *          used to prevent bright pixels with low saturation from being
 *          darkened.  Setting thresh == 0 is a no-op; setting %thresh == 255
 *          causes the darkening to be applied to all pixels.
 *      (3) This function is useful to enhance pixels relative to a
 *          gray background.
 *      (4) A related function that builds a 1 bpp mask over the gray
 *          pixels is pixMaskOverGrayPixels().
 * </pre>
 */
PIX *
pixDarkenGray(PIX     *pixd,
              PIX     *pixs,
              l_int32  thresh,
              l_int32  satlimit)
{
l_int32    w, h, i, j, wpls, wpld;
l_int32    rval, gval, bval, minrg, min, maxrg, max, sat;
l_uint32  *datas, *datad, *lines, *lined;
l_float32  ratio;

    PROCNAME("pixDarkenGray");

    if (!pixs || pixGetDepth(pixs) != 32)
        return (PIX *)ERROR_PTR("pixs undefined or not 32 bpp", procName, NULL);
    if (thresh < 0 || thresh > 255)
        return (PIX *)ERROR_PTR("invalid thresh", procName, NULL);
    if (satlimit < 1)
        return (PIX *)ERROR_PTR("invalid satlimit", procName, NULL);
    if (pixd && (pixs != pixd))
        return (PIX *)ERROR_PTR("not new or in-place", procName, NULL);

    pixGetDimensions(pixs, &w, &h, NULL);
    datas = pixGetData(pixs);
    wpls = pixGetWpl(pixs);
    if ((pixd = pixCopy(pixd, pixs)) == NULL)
        return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
    datad = pixGetData(pixd);
    wpld = pixGetWpl(pixd);

    for (i = 0; i < h; i++) {
        lines = datas + i * wpls;
        lined = datad + i * wpld;
        for (j = 0; j < w; j++) {
            extractRGBValues(lines[j], &rval, &gval, &bval);
            minrg = L_MIN(rval, gval);
            min = L_MIN(minrg, bval);
            maxrg = L_MAX(rval, gval);
            max = L_MAX(maxrg, bval);
            sat = max - min;
            if (max >= thresh || sat >= satlimit)
                continue;
            ratio = (l_float32)sat / (l_float32)satlimit;
            composeRGBPixel((l_int32)(ratio * rval), (l_int32)(ratio * gval),
                            (l_int32)(ratio * bval), &lined[j]);
        }
    }
    return pixd;
}


/*-----------------------------------------------------------------------*
 *            General multiplicative constant color transform            *
 *-----------------------------------------------------------------------*/
/*!
 * \brief   pixMultConstantColor()
 *
 * \param[in]    pixs     colormapped or rgb
 * \param[in]    rfact    red multiplicative factor
 * \param[in]    gfact    green multiplicative factor
 * \param[in]    bfact    blue multiplicative factor
 * \return  pixd colormapped or rgb, with colors scaled, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) rfact, gfact and bfact can only have non-negative values.
 *          They can be greater than 1.0.  All transformed component
 *          values are clipped to the interval [0, 255].
 *      (2) For multiplication with a general 3x3 matrix of constants,
 *          use pixMultMatrixColor().
 * </pre>
 */
PIX *
pixMultConstantColor(PIX       *pixs,
                     l_float32  rfact,
                     l_float32  gfact,
                     l_float32  bfact)
{
l_int32    i, j, w, h, d, wpls, wpld;
l_int32    ncolors, rval, gval, bval, nrval, ngval, nbval;
l_uint32   nval;
l_uint32  *datas, *datad, *lines, *lined;
PIX       *pixd;
PIXCMAP   *cmap;

    PROCNAME("pixMultConstantColor");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    cmap = pixGetColormap(pixs);
    if (!cmap && d != 32)
        return (PIX *)ERROR_PTR("pixs not cmapped or 32 bpp", procName, NULL);
    rfact = L_MAX(0.0, rfact);
    gfact = L_MAX(0.0, gfact);
    bfact = L_MAX(0.0, bfact);

    if (cmap) {
        if ((pixd = pixCopy(NULL, pixs)) == NULL)
            return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
        cmap = pixGetColormap(pixd);
        ncolors = pixcmapGetCount(cmap);
        for (i = 0; i < ncolors; i++) {
            pixcmapGetColor(cmap, i, &rval, &gval, &bval);
            nrval = (l_int32)(rfact * rval);
            ngval = (l_int32)(gfact * gval);
            nbval = (l_int32)(bfact * bval);
            nrval = L_MIN(255, nrval);
            ngval = L_MIN(255, ngval);
            nbval = L_MIN(255, nbval);
            pixcmapResetColor(cmap, i, nrval, ngval, nbval);
        }
        return pixd;
    }

    if ((pixd = pixCreateTemplate(pixs)) == NULL)
        return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
    datas = pixGetData(pixs);
    datad = pixGetData(pixd);
    wpls = pixGetWpl(pixs);
    wpld = pixGetWpl(pixd);
    for (i = 0; i < h; i++) {
        lines = datas + i * wpls;
        lined = datad + i * wpld;
        for (j = 0; j < w; j++) {
            extractRGBValues(lines[j], &rval, &gval, &bval);
            nrval = (l_int32)(rfact * rval);
            ngval = (l_int32)(gfact * gval);
            nbval = (l_int32)(bfact * bval);
            nrval = L_MIN(255, nrval);
            ngval = L_MIN(255, ngval);
            nbval = L_MIN(255, nbval);
            composeRGBPixel(nrval, ngval, nbval, &nval);
            *(lined + j) = nval;
        }
    }

    return pixd;
}


/*!
 * \brief   pixMultMatrixColor()
 *
 * \param[in]    pixs    colormapped or rgb
 * \param[in]    kel     kernel 3x3 matrix of floats
 * \return  pixd colormapped or rgb, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) The kernel is a data structure used mostly for floating point
 *          convolution.  Here it is a 3x3 matrix of floats that are used
 *          to transform the pixel values by matrix multiplication:
 *            nrval = a[0,0] * rval + a[0,1] * gval + a[0,2] * bval
 *            ngval = a[1,0] * rval + a[1,1] * gval + a[1,2] * bval
 *            nbval = a[2,0] * rval + a[2,1] * gval + a[2,2] * bval
 *      (2) The matrix can be generated in several ways.
 *          See kernel.c for details.  Here are two of them:
 *            (a) kel = kernelCreate(3, 3);
 *                kernelSetElement(kel, 0, 0, val00);
 *                kernelSetElement(kel, 0, 1, val01);
 *                ...
 *            (b) from a static string; e.g.,:
 *                const char *kdata = " 0.6  0.3 -0.2 "
 *                                    " 0.1  1.2  0.4 "
 *                                    " -0.4 0.2  0.9 ";
 *                kel = kernelCreateFromString(3, 3, 0, 0, kdata);
 *      (3) For the special case where the matrix is diagonal, it is easier
 *          to use pixMultConstantColor().
 *      (4) Matrix entries can have positive and negative values, and can
 *          be larger than 1.0.  All transformed component values
 *          are clipped to [0, 255].
 * </pre>
 */
PIX *
pixMultMatrixColor(PIX       *pixs,
                   L_KERNEL  *kel)
{
l_int32    i, j, index, kw, kh, w, h, d, wpls, wpld;
l_int32    ncolors, rval, gval, bval, nrval, ngval, nbval;
l_uint32   nval;
l_uint32  *datas, *datad, *lines, *lined;
l_float32  v[9];  /* use linear array for convenience */
PIX       *pixd;
PIXCMAP   *cmap;

    PROCNAME("pixMultMatrixColor");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (!kel)
        return (PIX *)ERROR_PTR("kel not defined", procName, NULL);
    kernelGetParameters(kel, &kw, &kh, NULL, NULL);
    if (kw != 3 || kh != 3)
        return (PIX *)ERROR_PTR("matrix not 3x3", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    cmap = pixGetColormap(pixs);
    if (!cmap && d != 32)
        return (PIX *)ERROR_PTR("pixs not cmapped or 32 bpp", procName, NULL);

    for (i = 0, index = 0; i < 3; i++)
        for (j = 0; j < 3; j++, index++)
            kernelGetElement(kel, i, j, v + index);

    if (cmap) {
        if ((pixd = pixCopy(NULL, pixs)) == NULL)
            return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
        cmap = pixGetColormap(pixd);
        ncolors = pixcmapGetCount(cmap);
        for (i = 0; i < ncolors; i++) {
            pixcmapGetColor(cmap, i, &rval, &gval, &bval);
            nrval = (l_int32)(v[0] * rval + v[1] * gval + v[2] * bval);
            ngval = (l_int32)(v[3] * rval + v[4] * gval + v[5] * bval);
            nbval = (l_int32)(v[6] * rval + v[7] * gval + v[8] * bval);
            nrval = L_MAX(0, L_MIN(255, nrval));
            ngval = L_MAX(0, L_MIN(255, ngval));
            nbval = L_MAX(0, L_MIN(255, nbval));
            pixcmapResetColor(cmap, i, nrval, ngval, nbval);
        }
        return pixd;
    }

    if ((pixd = pixCreateTemplate(pixs)) == NULL)
        return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
    datas = pixGetData(pixs);
    datad = pixGetData(pixd);
    wpls = pixGetWpl(pixs);
    wpld = pixGetWpl(pixd);
    for (i = 0; i < h; i++) {
        lines = datas + i * wpls;
        lined = datad + i * wpld;
        for (j = 0; j < w; j++) {
            extractRGBValues(lines[j], &rval, &gval, &bval);
            nrval = (l_int32)(v[0] * rval + v[1] * gval + v[2] * bval);
            ngval = (l_int32)(v[3] * rval + v[4] * gval + v[5] * bval);
            nbval = (l_int32)(v[6] * rval + v[7] * gval + v[8] * bval);
            nrval = L_MAX(0, L_MIN(255, nrval));
            ngval = L_MAX(0, L_MIN(255, ngval));
            nbval = L_MAX(0, L_MIN(255, nbval));
            composeRGBPixel(nrval, ngval, nbval, &nval);
            *(lined + j) = nval;
        }
    }

    return pixd;
}


/*-------------------------------------------------------------*
 *                    Half-edge by bandpass                    *
 *-------------------------------------------------------------*/
/*!
 * \brief   pixHalfEdgeByBandpass()
 *
 * \param[in]    pixs         8 bpp gray or 32 bpp rgb
 * \param[in]    sm1h, sm1v   "half-widths" of smoothing filter sm1
 * \param[in]    sm2h, sm2v   "half-widths" of smoothing filter sm2;
 *                            require sm2 != sm1
 * \return  pixd, or NULL on error
 *
 * <pre>
 * Notes:
 *      (1) We use symmetric smoothing filters of odd dimension,
 *          typically use 3, 5, 7, etc.  The smoothing parameters
 *          for these are 1, 2, 3, etc.  The filter size is related
 *          to the smoothing parameter by
 *               size = 2 * smoothing + 1
 *      (2) Because we take the difference of two lowpass filters,
 *          this is actually a bandpass filter.
 *      (3) We allow both filters to be anisotropic.
 *      (4) Consider either the h or v component of the 2 filters.
 *          Depending on whether sm1 > sm2 or sm2 > sm1, we get
 *          different halves of the smoothed gradients (or "edges").
 *          This difference of smoothed signals looks more like
 *          a second derivative of a transition, which we rectify
 *          by not allowing the signal to go below zero.  If sm1 < sm2,
 *          the sm2 transition is broader, so the difference between
 *          sm1 and sm2 signals is positive on the upper half of
 *          the transition.  Likewise, if sm1 > sm2, the sm1 - sm2
 *          signal difference is positive on the lower half of
 *          the transition.
 * </pre>
 */
PIX *
pixHalfEdgeByBandpass(PIX     *pixs,
                      l_int32  sm1h,
                      l_int32  sm1v,
                      l_int32  sm2h,
                      l_int32  sm2v)
{
l_int32  d;
PIX     *pixg, *pixacc, *pixc1, *pixc2;

    PROCNAME("pixHalfEdgeByBandpass");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (sm1h == sm2h && sm1v == sm2v)
        return (PIX *)ERROR_PTR("sm2 = sm1", procName, NULL);
    d = pixGetDepth(pixs);
    if (d != 8 && d != 32)
        return (PIX *)ERROR_PTR("pixs not 8 or 32 bpp", procName, NULL);
    if (d == 32)
        pixg = pixConvertRGBToLuminance(pixs);
    else   /* d == 8 */
        pixg = pixClone(pixs);

        /* Make a convolution accumulator and use it twice */
    if ((pixacc = pixBlockconvAccum(pixg)) == NULL) {
        pixDestroy(&pixg);
        return (PIX *)ERROR_PTR("pixacc not made", procName, NULL);
    }
    if ((pixc1 = pixBlockconvGray(pixg, pixacc, sm1h, sm1v)) == NULL) {
        pixDestroy(&pixg);
        pixDestroy(&pixacc);
        return (PIX *)ERROR_PTR("pixc1 not made", procName, NULL);
    }
    pixc2 = pixBlockconvGray(pixg, pixacc, sm2h, sm2v);
    pixDestroy(&pixg);
    pixDestroy(&pixacc);
    if (!pixc2) {
        pixDestroy(&pixc1);
        return (PIX *)ERROR_PTR("pixc2 not made", procName, NULL);
    }

        /* Compute the half-edge using pixc1 - pixc2.  */
    pixSubtractGray(pixc1, pixc1, pixc2);
    pixDestroy(&pixc2);
    return pixc1;
}
